1. Field of the Invention
The present invention relates to a liquid crystal display device in which a light conductor is disposed on a rear face side (rear surface) of a transmission type liquid crystal display element, which display element is illuminated, through the light conductor, with an internal light emitted from a light source or with an external light entering through a light transmitting window provided above the light conductor, and a display image as a virtual image reflected by a reflecting plate which is disposed inclinedly on a front face side of the liquid crystal display element, is seen.
2. Description of the Prior Art
In Japanese Utility Model Publication No. 53369/81 issued by the Japanese Patent Office there is disclosed a device in which light is directed to a transmission type liquid crystal display element from a rear side of the same element, then transmitted light is reflected by a reflecting plate, and a display image on the reflecting plate is seen from a display window formed in a frame.
This liquid crystal display device is used, for example, in a vehicle in such a mode as shown in FIG. 9, in which a transmission type liquid crystal display element 2 is attached horizontally to a vehicular hood 1 and on a front face side of the display element 2 there is disposed a reflecting plate 3 opposedly and inclinedly at a predetermined angle .theta. so that a reflected display image can be seen by a driver 4 as an observer, while on a rear face side of the liquid crystaI display element 2 is disposed a light conductor 6 through a color filter. When the surroundings are dark, for example, during the night, an internal light from a light source 7 is conducted by the light conductor 6 and passes through the color filter 5, while when the surroundings are light, for example, during the daytime, an external light entering from a front glass 8 passes through the light conductor 6 and the color filter 5 through a diffusion plate 10 fitted in a light transmitting window 9 which is formed in an upper surface of the hood 1, thereby illuminating the liquid crystal display element 2.
Futher, on a rear face side of the light conductor 6, that is, on the side of the light conductor 6 opposite to its side facing the liquid crystal display element 2, there is provided a semi-transmissibIe reflection member 11, e.g. a half mirror or a bright color ink layer, with a view to not only reflecting the internal light incident on the interior of the light conductor 6 from the light source 7, positively toward the liquid crystal display element 2 but also transmitting the external light to the same side.
In this liquid crystal display device, a virtual image on the reflecting plate 3 is seen, so in comparison with a display device of the type in which the liquid crystal display element 2 is seen directly, the display image so far reflected toward the observer may deviate largely due to a slight dislocation of the display element 2 or the reflecting plate 3, and thus it is difficult to effect positioning. Particularly, where the liquid crystal display device is to be incorporated in a vehicular meter which undergoes frequent vibrations, since in the above prior art the liquid crystal display element 2 and the reflecting plate 3 are fixed separately to the meter case, it is difficult to set the angle .theta. between the display element 2 and the reflecting plate 3 at the time of assembly, or the said angle .theta. may vary due to vibrations or distortion of the meter case even after assembly and in this case there is fear that the display image will not be reflected toward the eyes of the driver 4
If the light source 7 is turned ON during the night, not only this light will be reflected toward the liquid crystal display element 2 by the light conductor 6 but also a portion thereof will pass through the semi-transmissible reflection member 11 and leak above toward the diffusion plate 10, so that the diffusion plate 10 lights, or the light passes through the diffusion plate and is reflected on the front glass 8, thus obstructing the sight of the driver 4.